import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User:
 * Date: 2025-06-14
 * Time: 20:48
 */
public class TcpEchoServer {
    private ServerSocket serverSocket = null;

    public TcpEchoServer(int port) throws IOException {
        serverSocket = new ServerSocket(port);
    }

    public void start() throws IOException {
        System.out.println("启动服务器");

        ExecutorService executorService = Executors.newCachedThreadPool();

        while(true){
            //tcp来说，需要优先处理客户端发来的连接
            //通过读写 clientSocket，和客户端进行通信
            //如果没有客户端发起连接，此时accept就会阻塞

            //主线程负责进行accept，每次accpet到一个客户端，就创建一个线程，由新线程负责处理客户端的请求
            Socket clientSocket = serverSocket.accept();


            executorService.submit(() -> {
                processConnection(clientSocket);
            });
        }
    }

    private void processConnection(Socket clientSocket) {
        System.out.printf("[%s, %d], 客户端上线！\n", clientSocket.getInetAddress(), clientSocket.getPort());
        try(InputStream inputStream = clientSocket.getInputStream();
            OutputStream outputStream = clientSocket.getOutputStream()) {
            //针对 InputStream套了一层
            Scanner scanner = new Scanner(inputStream);
            //针对 OutputStream 套了一层
            PrintWriter writer = new PrintWriter(outputStream);
            //分成三个步骤
            while(true){
                //1.读取请求并解析，可以直接read，也可以借助Scanner来辅助完成
                if(!scanner.hasNext()){
                    System.out.printf("[%s:%d] 客户端下线！\n", clientSocket.getInetAddress(), clientSocket.getPort());
                    break;
                }
                String request = scanner.next();
                //2.根据请求计算响应
                String response = process(request);
                //3.返回响应到客户端
                writer.println(response);
                writer.flush();//刷新缓存区

                //打印日志
                System.out.printf("[%s:%d] req: %s, resp: %s\n", clientSocket.getInetAddress(), clientSocket.getPort(), request, response);

            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                clientSocket.close();
            } catch (IOException e) {
                throw  new RuntimeException();
            }
        }
    }

    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        TcpEchoServer server = new TcpEchoServer(9090);
        server.start();
    }
}
